Iris Coloboma

Iris coloboma is a congenital deformity caused by a localized developmental abnormality of the iris involving all iris layers. A coloboma may be located at the pupillary margin, at the iris base as an atypical coloboma, or on the ventronasal iris when it results from failure of closure of the optic fissure, termed a typical coloboma.

Iris coloboma may occur as an isolated abnormality or together with other ocular anomalies, such as as part of hereditary Collie Eye Anomaly (CEA) in Collies and Australian Shepherds. It appears as an iris defect resembling a scratch or a variably shaped spot. If the defect lies adjacent to the pupil, the combination of pupil and defect may create a keyhole configuration or otherwise produce an abnormally shaped pupil.

Treatment

Diagnosis is made by ophthalmic examination. No treatment is performed.

Iris coloboma in a dog. A crescent-shaped defect is visible in the iris adjacent to the pupil.

Iris coloboma in a dog.

Adapted from the Atlas of Ocular Diseases in Dogs and Cats by Dr. Siniša D. Grozdanić and colleagues. © Animal Eye Consultants of Iowa. The text and clinical images on this page are original content from the authors' own clinical practice and research, and may not be reproduced, distributed, or repurposed without permission.

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